Use of time variant digital sigma-delta for fractional frequency synthesizers

This paper proposes a new low order time variant digital ΣΔ MASH modulator for fractional frequency synthesizers. The phase noise spectrum is improved as the spur tones from the fractional modulation are disabled. The usage of low order time variant MASH architectures reduces the number of levels that control the programable divider, reducing therefore the complexity and power requirements of the synthesizer.